Technical guidelines in numerical calculation of the scattering parameters in filled three dimensional waveguide structures

Scattering parameters are the most widely used tools for characterization of the linear microwave circuits. Although they can be physically measured after the implementation of the microwave circuits, accurate calculation of these parameters plays a crucial role in the design process. By using a time domain technique such as finite difference time domain, it is possible to calculate the scattering parameters in wide frequency range efficiently. This paper presents a detailed step by step procedure for numerical calculation of the scattering parameters in three dimensional waveguide structures which include a general type of scattering object inside them using finite difference time domain technique. Technical recipes for efficient and accurate calculations are provided for source excitation, 3-D PML absorbing boundary condition and S-parameter extraction method.